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2.8 to 3.4 Engine Swap. Help needed.

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Old 09-14-2018, 06:18 PM   #1  
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2.8 to 3.4 Engine Swap. Help needed.

Well, it's been awhile since I posted on here. My 2.8 had racked up over 600k miles on it and was losing compression and therefore power. After much contemplation, I decided to do the 3.4 swap boogie. I was actually surprised at how good my old engine looked as I disassembled it. I started in June, but I'm only able to work on it about 5 or 6 hours a week due to other obligations.

Note: I have a 1984 Firebird with a carb.

After much trouble, I got everything in and was ready to crank the new engine. However, it won't... This is my first engine swap, so maybe I'm missing something obvious. When I try to crank it, it sounds like it wants to start, but then puffs and flames shoot out of the carb. I definitely have fuel and spark, both tested independently and verified by the flames. I put the distributor in on #1 TDC, but I haven't been able to set the timing exactly since it won't crank. Thanks in advance for any help.
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Old 09-14-2018, 06:45 PM   #2  
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Re: 2.8 to 3.4 Engine Swap. Help needed.

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Originally Posted by Liboicl View Post
Well, it's been awhile since I posted on here. My 2.8 had racked up over 600k miles on it and was losing compression and therefore power. After much contemplation, I decided to do the 3.4 swap boogie. I was actually surprised at how good my old engine looked as I disassembled it. I started in June, but I'm only able to work on it about 5 or 6 hours a week due to other obligations.

Note: I have a 1984 Firebird with a carb.

After much trouble, I got everything in and was ready to crank the new engine. However, it won't... This is my first engine swap, so maybe I'm missing something obvious. When I try to crank it, it sounds like it wants to start, but then puffs and flames shoot out of the carb. I definitely have fuel and spark, both tested independently and verified by the flames. I put the distributor in on #1 TDC, but I haven't been able to set the timing exactly since it won't crank. Thanks in advance for any help.
Sounds like your 180 degrees off on your distributor timing . Remember , for each complete cycle , the piston is actually at TDC twice , once on the compression stroke and once on the exhaust stroke . If your timed on the exhaust stroke instead of the compression stroke the classic telltale is exactly what you describe "puffs and flames shoot out of the carb" and an engine that won't run .

Bottom line = make sure your timed to the compression and not the exhaust stroke .....
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Old 09-14-2018, 06:50 PM   #3  
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Re: 2.8 to 3.4 Engine Swap. Help needed.

Did you disconnect the timing wire? Happened to me once I forgot to disconnect.
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Old 09-14-2018, 07:13 PM   #4  
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Re: 2.8 to 3.4 Engine Swap. Help needed.

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Sounds like your 180 degrees off on your distributor timing . Remember , for each complete cycle , the piston is actually at TDC twice , once on the compression stroke and once on the exhaust stroke . If your timed on the exhaust stroke instead of the compression stroke the classic telltale is exactly what you describe "puffs and flames shoot out of the carb" and an engine that won't run .

Bottom line = make sure your timed to the compression and not the exhaust stroke .....
I was very careful with that. I had the valve cover off to watch for them both to close and had my finger over the hole with the spark plug out and had it blown off the hole. Even still, I had tried flipping it 180 degrees to see and it doesn't shoot flames, but it doesn't even sound like it tries to start. It just turns over repeatedly.

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Did you disconnect the timing wire? Happened to me once I forgot to disconnect.
I'm not sure, but I don't think this applies. I should disconnect it to crank it? I can understand doing that if I'm setting timing, but on the first crank?
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Old 09-15-2018, 12:41 AM   #5  
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Re: 2.8 to 3.4 Engine Swap. Help needed.

Yeah, disconnecting the bypass wire doesn't apply to a carb'd car...

Since you say you're on compression stroke...

What firing order are you using, and which way around the cap are you going when connecting the cylinders in order?
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Old 09-15-2018, 01:46 AM   #6  
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Re: 2.8 to 3.4 Engine Swap. Help needed.

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Originally Posted by Six_Shooter View Post
Yeah, disconnecting the bypass wire doesn't apply to a carb'd car...

Since you say you're on compression stroke...

What firing order are you using, and which way around the cap are you going when connecting the cylinders in order?
Clockwise:165432
Counter:123456
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Old 09-15-2018, 08:16 PM   #7  
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Re: 2.8 to 3.4 Engine Swap. Help needed.

As I suspected, you're not using the correct firing order... (That firing order is for a 4.3...)

The firing order is 1-2-3-4-5-6, yes, really, it's 1-2-3-4-5-6. IIRC the dizzy rotates clockwise (I've had DIS for far longer than I had a dizzy equipped 60 degree V6...)
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Old 09-15-2018, 08:23 PM   #8  
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Re: 2.8 to 3.4 Engine Swap. Help needed.

Well, I looked it up when I was putting it back on and found this image on Google search https://www.thirdgen.org/forums/tech...ml#post4815656, but after reading the forum post, and looking closer, it seems that was for a different engine. Hmm. Well, I won't get to mess with it for a couple of weeks, but I sure hope that fixes it. I should pay more attention sometimes.
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